Method of recognizing conveyor belt wear condition

ABSTRACT

A method of recognizing a conveyor belt wear condition is provided. Relationships between an apparent compressive stress in a wear resistance test and surface roughness of a sample and between the surface roughness and amount of wear per unit frictional energy of the sample are acquired. A wear condition of an upper cover rubber is recognized based on an apparent compressive stress generated on the upper cover rubber at a use site, and a database is created based on the relationships. Alternatively, relationships between an average wear pitch calculated from the surface roughness and viscoelastic properties of the sample and between the average wear pitch and an actual amount of wear of the sample are acquired. A wear condition of the upper cover rubber is recognized based on the viscoelastic properties of the upper cover rubber of the use site and a database is created based on the relationships.

TECHNICAL FIELD

The present technology relates to a method of recognizing a conveyorbelt wear condition, and particularly relates to a method of recognizinga conveyor belt wear condition where a wear condition of an upper coverrubber at a conveyor belt use site can be accurately recognized based onthe results of a wear resistance evaluation test using a sample.

BACKGROUND ART

Various objects including iron ore, limestone, and other mineralresources are conveyed by conveyor belts. When being conveyed by theconveyor belt, an object to be conveyed is fed onto an upper coverrubber of the conveyor belt from a hopper or another conveyor belt. Thefed object to be conveyed is loaded on the upper cover rubber andconveyed in a traveling direction of the conveyor belt. When the objectto be conveyed is loaded on the upper cover rubber and conveyed, theupper cover rubber is subject to wear as a result of the object to beconveyed sliding on the upper cover rubber. The amount of wear generatedon the upper cover rubber due to the fed object to be conveyed greatlychanges based on the specification and use conditions of the conveyorbelt.

Evaluation methods using a Pico abrasion test, DIN (German Institute forStandardization) abrasion test, Lambourn abrasion test, Taber abrasiontest, Williams abrasion test, Akron abrasion test, or the like are knownas methods of evaluating rubber wear resistance. Furthermore, evaluationmethods using a wear testing device for a conveyor belt was alsoproposed (for example, refer to Japanese Unexamined Patent ApplicationPublication No. 2004-20319). With these evaluation methods, the amountof wear of a worn rubber sample is measured by pressing a pressing bodyagainst a rubber sample while relatively moving both. However, the wearresistance obtained by these conventional evaluation methods and actualwear resistance of a conveyor belt at a use site greatly deviate.Therefore, evaluation methods using a rubber sample have a problem wherea wear condition of a conveyor belt at a use site can not be accuratelyrecognized.

SUMMARY

The present technology provides a method of recognizing a conveyor beltwear condition where a wear condition of an upper cover rubber at a usesite can be accurately recognized based on the results of a wearresistance evaluation test using a sample.

A method of recognizing a conveyor belt wear condition according to thepresent technology includes the steps of: performing a rubber wearresistance test using a sample for each rubber type, by varying apparentcompressive stress generated by a pressing force applied to the sample;acquiring a relationship between the apparent compressive stress and asurface roughness of the sample obtained from the test; acquiring arelationship between the surface roughness and an amount of wear perunit frictional energy of the sample obtained by the test; creating adatabase showing a correlation between the surface roughness, theapparent compressive stress, and the amount of wear per unit frictionalenergy based on the acquired relationships; and recognizing a wearcondition of an upper cover rubber at a conveyor belt use site, based onthe database and apparent compressive stress generated by a pressingforce provided by an object to be conveyed with regard to the uppercover rubber.

Another method of recognizing a conveyor belt wear condition accordingto the present technology includes the steps of: performing a rubberwear resistance test using a sample for a plurality of rubber types withdifferent viscoelastic properties; acquiring a relationship between anaverage wear pitch calculated from a surface roughness of the sampleobtained by the test and viscoelastic properties of the rubber type ofthe sample; acquiring a relationship between the average wear pitch andan actual amount of wear of the sample obtained by the test; creating adatabase showing a correlation between the average wear pitch, theviscoelastic properties, and the actual amount of wear of the sample;and recognizing a wear condition of the upper cover rubber based on thedatabase, the average wear pitch of an upper cover rubber of a conveyorbelt, and viscoelastic properties of the rubber type of the upper coverrubber.

With the present technology, an actual wear condition of an upper coverrubber of a conveyor belt is recognized based on the results of a rubberwear resistance evaluation test of using a sample. At this time,attention is given to rubber surface roughness generated due to wear.

In rubber subject to friction, a correlation between rubber surfaceroughness and apparent compressive stress generated by a pressing forceprovided on the rubber is high, and a correlation between rubber surfaceroughness and amount of wear per unit frictional energy of rubbersubject to friction is high. Therefore, a correlation between apparentcompressive stress and amount of wear per unit frictional energy is alsohigh. Therefore, with the former method of recognizing a conveyor beltwear condition according to the present technology, a wear condition ofan upper cover rubber at a use site can be accurately recognized basedon a database showing a correlation between the surface roughness, theapparent compressive stress, and the amount of wear per unit frictionalenergy, and based on the apparent compressive stress generated on theupper cover rubber cover at a conveyor belt use site.

Furthermore, in rubber subject to friction, a correlation betweenviscoelastic properties of the rubber and average wear pitch calculatedfrom the rubber surface roughness is high, and a correlation between anactual amount of wear of rubber and average wear pitch is high.Therefore, a correlation between viscoelastic properties of the rubberand actual amount of wear is also high. Therefore, with the lattermethod of recognizing a conveyor belt wear condition according to thepresent technology, a wear condition of an upper cover rubber at a usesite can be accurately recognized based on a database showing acorrelation between the average wear pitch, the viscoelastic properties,and the actual amount of wear, and based on the viscoelastic propertiesof the upper cover rubber of the conveyor belt, and based on an averagewear pitch of the upper rubber cover.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an explanatory diagram illustrating a conveyor belt line in asimplified manner.

FIG. 2 is a cross-sectional view taken along A-A of FIG. 1.

FIG. 3 is an explanatory diagram illustrating a friction force appliedon a conveyor belt.

FIG. 4 is an explanatory diagram illustrating a basic structure of awear testing device.

FIG. 5 is an explanatory diagram illustrating a system that recognizes awear condition of a conveyor belt.

FIG. 6 is an explanatory diagram illustrating a wear line formed on asurface of a sample.

FIG. 7 is a graph showing a surface roughness of a sample.

FIG. 8 is a graph showing a relationship between surface roughness andapparent compressive stress generated on a sample.

FIG. 9 is a graph showing a relationship between an amount of wear perunit frictional energy and surface roughness of a sample.

FIG. 10 is a graph showing a relationship between apparent compressivestress generated on a sample and amount of wear per unit frictionalenergy.

FIG. 11 is a graph showing a relationship between viscoelasticproperties and average wear pitch of a sample.

FIG. 12 is a graph showing a relationship between average wear pitch andactual amount of wear of a sample.

DETAILED DESCRIPTION

A method of recognizing a conveyor belt wear condition according to thepresent technology will be described below based on embodimentsillustrated in the drawings.

In a conveyor belt line illustrated in FIG. 1, an object to be conveyedC conveyed by another conveyor belt 7 is fed onto a conveyor belt 1 andconveyed to a conveying destination by the conveyor belt 1. The objectto be conveyed C may be fed onto the conveyor belt 1 by a hopper or thelike. The conveyor belt 1 is stretched at a predetermined tensionbetween pulleys 5 a and 5 b.

As illustrated in FIG. 2, the conveyor belt 1 is configured from: a corelayer 2 formed from a core as canvas, steel cord, or the like; and anupper cover rubber 3 and a lower cover rubber 4 that sandwich the corelayer 2. The core layer 2 is a member bearing a tension that stretchesthe conveyor belt 1. The lower cover rubber 4 is supported by a supportroller 6 on a carrier side of the conveyor belt 1, and the upper coverrubber 3 is supported in a flat shape by the support roller 6 on areturn side of the conveyor belt 1. Three of the support rollers 6 arearranged on the carrier side of the conveyor belt 1 in a belt widthdirection. The conveyor belt 1 is supported by the support rollers 6 ina concave shape having a predetermined trough angle a. When the pulley 5a on a drive side is rotationally driven, the conveyor belt 1 isoperated in one direction at a predetermined traveling speed V1. Theobject to be conveyed C is fed onto the upper cover rubber 3, loaded onthe upper cover rubber 3, and then conveyed.

In the conveyor belt line, as illustrated in FIG. 3, the conveyor belt 1and the other conveyor belt 7 are arranged at a vertical difference h(difference h in height positions of conveying surfaces of the conveyorbelts). The object to be conveyed C is conveyed at a speed V0 (V0<V1) ina horizontal direction on the other conveyor belt 7. At the moment thatthe object to be conveyed C is loaded on the conveyor belt 1 from theother conveyor belt 7, the object to be conveyed C remains at the speedV0 in a horizontal direction, but is conveyed by the conveyor belt 1,and therefore, the speed in the horizontal direction thereof graduallyreaches the same speed V1 as the traveling speed of the conveyor belt 1.

In other words, the object to be conveyed C contacting the upper coverrubber 3 moves at a relative moving speed V (=V1−V0) in a travelingdirection with regard to the conveyor belt 1 while generating acompressive stress Pr on the upper cover rubber 3, and the finalrelative moving speed V is zero. During this time, a friction force facts on the upper cover rubber 3, and the upper cover rubber 3 primarilywears due to this behavior of the object to be conveyed C.

The apparent compressive stress Pr generated on the upper cover rubber 3by the object to be conveyed C is a pressing force (can be regarded asweight W of the object to be conveyed C) where the object to be conveyedC presses the upper cover rubber 3 with regard to a contact area Arbetween the object to be conveyed C and the upper cover rubber 3. Inother words, apparent compressive stress Pr=weight W of object to beconveyed C/contact area Ar.

As illustrated in FIG. 4, a rubber wear testing device 8 is generallyprovided with a pressing body 9, a pressing mechanism 10 that pressesthe pressing body 9 against a rubber sample S, and a relative movementmechanism 11 that relatively moves the pressing body 9 and sample S.With a wear resistance testing method using the testing device 8, wearis generated on the sample S by relatively moving the pressing body 9while pressing against the sample S to recognize the amount of wear andwear mode. Furthermore, with the aforementioned conventional weartesting method, the specifications of the pressing body 9, pressingmechanism 10, and relative movement mechanism 11 are all different.

With the present technology, a conventional wear resistance test isconducted using the sample S to acquire data. A Pico abrasion test, DINabrasion test, Lambourn abrasion test, Taber abrasion test, Williamsabrasion test, Akron abrasion test, or the like can be used as theconventional wear resistance test. Furthermore, a system 12 illustratedin FIG. 5, for example, is used to recognize a wear condition of theconveyor belt. The system 12 is provided with a calculation device 13where a database D1, D2 created based on data acquired by a test isstored, an input unit 14 that inputs data into the calculation device13, and a display unit 15 that displays calculation results based on thecalculation device 13.

In order to create the database D1, a conventional wear resistance testis conducted using the sample S on a plurality of rubber types. Duringthe test, an apparent compressive stress Pe generated by a pressingforce provided on the sample S is varied, and a relationship between theapparent compressive stress Pe and a surface roughness R of the sample Sobtained by the test is acquired. A wear line L is formed on a surfaceof the samples S based on the test at intervals in a friction directionFD as illustrated in FIG. 6. The surface roughness R of the sample S isas shown in FIG. 7. In FIG. 7, an arithmetic mean roughness Ra asspecified in JIS (Japanese Industrial Standards) is used as the surfaceroughness R. The surface roughness R can also be a maximum height (Ry),ten-point mean roughness (Rz), or the like in addition to the arithmeticmean roughness Ra.

Conventional wear resistance tests have varying apparent compressivestresses Pe generated on the sample S, and therefore, if a plurality ofdifferent conventional wear resistance tests are conducted, a wearresistance test is conducted by varying the apparent compressive stressPe. For example, the apparent compressive stress Pe is 0.05 N/mm², 138.5N/mm², and 0.333 N/mm² in a DIN abrasion test, Pico abrasion test, andLambourn abrasion test, respectively. At least one of the DIN abrasiontest or Pico abrasion test is preferably used as the wear resistancetest.

The acquired relationship between the apparent compressive stress Pe andsurface roughness R has a high correlation as shown in FIG. 8. FIG. 8 isa semilogarithm graph, and data obtained by performing three differenttypes of wear resistance tests using three types of samples S1, S2, andS3 with different types of rubber are shown. In FIG. 8, the apparentcompressive stress Pe on a vertical axis is indicated by an index value,and as the index value increases, the apparent compressive stress Peincreases. As the apparent compressive stress Pe increases as shown inFIG. 8, the surface roughness R (surface roughness Ra in FIG. 8)increases.

A relationship between the surface roughness R and an amount of wear K1per unit frictional energy of the sample S acquired by the test isfurther acquired by a conventional wear resistance test. The amount ofwear K1 is calculated based on an actual amount of wear Vr of the sampleS/(contact area between the sample S and pressing body 9×rubber tensilestrength TB of the sample S×friction distance).

The acquired relationship between the surface roughness R and amount ofwear K1 has a high correlation as shown in FIG. 9. In FIG. 9, the amountof wear K1 on a vertical axis is indicated by an index value, and as theindex value increases, the amount of wear K1 increases. In other words,as the surface roughness R increases, the amount of wear K1 increases.In FIG. 9, the amount of wear K1 is used, but an amount of unit contactarea wear K2 can be used instead. The amount of unit contact area wearK2 is calculated based on the actual amount of wear Vr of the sampleS/(contact area between the sample S and pressing body 9). The acquiredrelationship between the surface roughness R and amount of wear K2 alsohas a high correlation similar to the acquired relationship between thesurface roughness R and amount of wear K1.

A relationship between the apparent compressive stress Pe and amount ofwear K1 can be acquired based on the relationships shown in FIG. 8 andFIG. 9 acquired by the test. The relationship between the apparentcompressive stress Pe and amount of wear K1 also has a high correlationas shown in the semilogarithm graph of FIG. 10. In other words, as theapparent compressive stress Pe increases, the amount of wear K1increases. Furthermore, the database D1 showing a correlation betweenthe surface roughness R, apparent compressive stress Pr, and amount ofwear K1 per unit frictional energy is created based on the acquiredrelationships shown in FIGS. 8, 9, and 10.

In order to recognize a wear condition of the upper cover rubber 3 ofthe conveyor belt 1 at a use site using the database D1, the apparentcompressive stress Pr generated by a pressing force provided by theobject to be conveyed C with regard to the upper cover rubber 3 at a usesite is input into the calculation unit 13 from the input unit 14illustrated in FIG. 5. Other already known data is preferably input inadvance in the calculation unit 13. The calculation unit 13 displays onthe display unit 15 a wear condition of the upper cover rubber 3 basedon the database D1 and input apparent compressive stress Pr. A wearcondition of the upper cover rubber 3 can be recognized by viewing thedetails displayed on the display unit 15.

For example, when recognizing a wear condition of the upper cover rubber3 of a certain conveyor belt 1, the apparent compressive stress Prgenerated on the upper cover rubber 3 at a use site is acquired and theninput into the calculation unit 13. The conditions of the use site ofthe conveyor belt 1 is already known, and therefore, the apparentcompressive stress Pr can be acquired by calculating from the alreadyknown conditions.

Next, in the data shown in FIG. 10, the wear amount of wear K1 per unitfrictional energy of the upper cover rubber 3 is calculated bysubstituting the index value of the apparent compressive stress Prgenerated on the upper cover rubber 3 for the apparent compressivestress Pe, using data for the same type of rubber as the upper coverrubber 3. The calculated amount of wear K1 per unit frictional energy iscalculated based on the aforementioned equation, and therefore, anactual amount of wear X of the upper cover rubber 3 at a use site can becalculated based on the amount of wear K1 and the contact area Arbetween the upper cover rubber 3 and object to be conveyed C at a usesite. In other words, the amount of wear X of the upper cover rubber 3can be displayed on the display unit 15 and recognized.

Alternatively, when recognizing the upper cover rubber 3 of a certainconveyor belt 1, the surface roughness R (Ra) of the upper cover rubber3 at a use site is acquired and then input into the calculation unit 13.Next, in the data shown in FIG. 9, the wear amount of wear K1 per unitfrictional energy of the upper cover rubber 3 is calculated bysubstituting the index value of the surface roughness Ra of the uppercover rubber 3 at a site for the surface roughness Ra, using data forthe same type of rubber as the upper cover rubber 3. The calculatedamount of wear K1 per unit frictional energy is calculated based on theaforementioned equation, and therefore, an amount of wear X of the uppercover rubber 3 at a use site can be calculated based on the amount ofwear K1 and the contact area Ar between the upper cover rubber 3 andobject to be conveyed C at a use site. Generally matching data isobtained for the calculated amount of wear X and the actual amount ofwear X where the upper cover rubber 3 was actually measured.

In order to create the other database D2, a conventional wear resistancetest is conducted using the sample S on a plurality of rubber types withdifferent viscoelastic properties RRF (Rolling Resistance Factor).Furthermore, a relationship between the average wear pitch P calculatedfrom the surface roughness R of the sample S obtained by the test andthe viscoelastic properties RRF of the type or rubber of the sample S.The average wear pitch P is an interval of the wear lines L adjacent inthe friction direction FD as illustrated in FIG. 6.

The relationship between the average wear pitch P and the viscoelasticproperties RRF has a high correlation as shown in FIG. 11. In FIG. 11,data obtained by performing three different types of wear resistancetests E1, E2, and E3 using three types of samples S1, S2, and S3 withdifferent types of rubber are described. In FIG. 11, the average wearpitch P on a vertical axis is indicated by an index value, and as theindex value increases, the average wear pitch P increases. Furthermore,RRF under a condition of 20° C. is used as the viscoelastic propertiesRRF on a horizontal axis in FIG. 11 is an indicator expressing dynamicvisco-elasticity of rubber, and as the index value decreases, therebound speed of the rubber increases, and response delay can bereduced, indicating that performance is excellent. The average wearpitch P varies based on the rubber type as shown in FIG. 11, and as theviscoelastic properties RRF of rubber increases, the average wear pitchP increases.

A relationship between the average wear pitch P and an actual amount ofwear Vr of the sample S obtained by the test is further acquired by aconventional wear resistance test. The relationship between the averagewear pitch P and actual amount of wear Vr has a high correlation asshown in FIG. 12, and as the average wear pitch P increases, the actualamount of wear Vr of the sample S increases. In FIG. 12, the actualamount of wear Vr on a vertical axis is indicated by an index value, andas the index value increases, the actual amount of wear Vr increases.

A relationship between the viscoelastic properties RRF and actual amountof wear Vr can be acquired based on the relationships shown in FIG. 11and FIG. 12 acquired by the test. Furthermore, the database D2 showing acorrelation between the average wear pitch P of the sample S,viscoelastic properties RRF, and actual amount of wear Vr is createdbased on the acquired relationships shown in FIGS. 11 and 12.

In order to recognize a wear condition of the upper cover rubber 3 ofthe conveyor belt 1 at a use site using the database D2, the rubber type(viscoelastic properties RRF) of the upper cover rubber 3 used in theconveyor belt 1 and the average wear pitch P of the upper cover rubber 3at a use site are input in the calculation unit 13 from the input unit14 illustrated in FIG. 5.

Next, in the data shown in FIG. 12, the amount of wear X of the uppercover rubber 3 is calculated by substituting the index value of theaverage wear pitch P of the upper cover rubber 3 at a use site for theaverage wear pitch P, using data for the same type of rubber (sameviscoelastic properties RRF) as the upper cover rubber 3. In otherwords, the calculated amount of wear X of the upper cover rubber 3 canbe displayed on the display unit 15 and recognized. Generally matchingdata is obtained for the calculated amount of wear X and the actualamount of wear X where the upper cover rubber 3 was actually measured.

Alternatively, the viscoelastic properties RRF or a rubber type used inthe upper cover rubber 3 are input in the calculation unit 13 from theinput unit 14 illustrated in FIG. 5. Furthermore, the extent of theaverage wear pitch P can be recognized based on the input viscoelasticproperties RRF and the data in FIG. 11.

The database D1, D2 are stored in the calculation unit 13 in theembodiment, but in the present technology, one of the database D1, D2may be stored in the calculation unit 13.

The invention claimed is:
 1. A method of recognizing a conveyor beltwear condition, comprising the steps of: performing a rubber wearresistance test using a sample for each rubber type, by varying apparentcompressive stress generated by a pressing force applied to the sample;acquiring a relationship between the apparent compressive stress and asurface roughness of the sample obtained from the test; acquiring arelationship between the surface roughness and an amount of wear perunit frictional energy of the sample obtained by the test; creating adatabase showing a correlation between the surface roughness, theapparent compressive stress, and the amount of wear per unit frictionalenergy based on the acquired relationships; and recognizing a wearcondition of an upper cover rubber at a conveyor belt use site, based onthe database and apparent compressive stress generated by a pressingforce provided by an object to be conveyed with regard to the uppercover rubber.
 2. The method of recognizing a conveyor belt wearcondition according to claim 1, wherein an arithmetic mean roughness Rais used as the surface roughness.
 3. The method of recognizing aconveyor belt wear condition according to claim 1, wherein at least oneof a DIN abrasion test and Pico abrasion test is used as the wearresistance test.